Microbial dynamics across tri-trophic systems: insights from plant–herbivore–predator interactions

Microbes play a critical role in regulating tri-trophic interactions among plants, herbivores, and their natural enemies, influencing key ecological and evolutionary processes. To fully understand these interactions through the food chain, a well-defined tri-trophic system is required. We investigated microbial dynamics involving plants (beans, cucumbers, and eggplants), spider mites (Tetranychus urticae), and predatory mites (Phytoseiulus persimilis) through 16S rRNA gene sequencing. The results revealed significant variations in microbiota across different trophic levels. Source tracking analysis indicated that microbiota at each trophic level were rarely inherited from the previous one, and deterministic processes played a key role in shaping the endosphere communities of these levels. Most shared zero-radius operational taxonomic units across each trophic level belonged to Pseudomonas, Bacillus, and Staphylococcus. Leaf microbiota differed among plants, while spider mites harbored similar microbiota. Notably, the microbiota of predatory mites on eggplants differed significantly from those on the other two plants. Biomarker selection and correlation analyses revealed that the abundance of Methylobacterium and Stenotrophomonas was strongly correlated with the improved fitness of predatory mites across different plants. Our study highlights the complex and dynamic nature of microbial communities across different trophic levels in a well-defined plant-herbivore-predator system.